{
  "bibcode": "2001GCN...934....1R",
  "body": "G. Ricker, D. Lamb, and S. Woosley on behalf of the HETE Science Team;\n\nR. Vanderspek, G. Crew, J. Doty, G. Monnelly, J. Villasenor; N. \nButler, T. Cline, J.G. Jernigan, A. Levine, F. Martel, G. Pizzichini, \nand G. Prigozhin, on behalf of the HETE Operations and HETE \nOptical-SXC Teams;\n\nN. Kawai, M. Matsuoka, Y. Shirasaki, T. Tamagawa, A. Yoshida, E. \nFenimore, M. Galassi, and  C. Graziani, on behalf of the HETE WXM \nTeam;\n\nJ-L Atteia, M. Boer, J-F Olive, J-P Dezalay, and K. Hurley on behalf \nof the HETE FREGATE Team;\n\nwrite:\n\nOn 13 February 2001 at 12:35:35 UTC, a soft spectrum, high energy \ntransient at high galactic latitude was detected and localized by \nHETE.  Both the WXM and the FREGATE instruments detected the event. \nAlthough the WXM and FREGATE cover extremely broad energy bands (WXM: \n2-25 keV; FREGATE: 6-500 keV), the burst event was only detectable in \nthe 2-18 keV band by WXM, and in the 6-10 keV band by FREGATE. \nBecause of the unusual spectrum of the transient, neither instrument \ntriggered.\n\nThe preliminary coordinates of the burst are RA= 10h 31m 36s, Dec= \n+5d 30' 39\" (J2000), derived from combining data from the WXM and \nBoresighted Optical Cameras.  The statistical error radius in the WXM \nlocalization is 3.5 arcmin (95% confidence).  In addition, we estimate \na systematic error radius at present of 30 arcmin about this \nlocation.  The spacecraft aspect was known to an accuracy of +/- 30 \narcsec (95% confidence) from the optical cameras, and will be \nimproved.\n\nThe burst exhibited a double-peaked structure and lasted about 30 \nseconds.  The incident flux measured with the WXM (2-18 keV) at the \nfirst peak is about 0.7 Crab, and at the second peak is about 2.4 \nCrab.  The spectrum in the 2-18 keV range was harder than that of the \nCrab nebula at the first peak, and softer than that of the Crab at \nthe second peak.  The peak flux seen with FREGATE (6-10 keV) was ~2\nCrab.  Assuming a Crab-like spectrum, the peak energy flux was ~1.5\nE-8 erg/cm^2/sec in the 6-10 keV range.\n\nThe high galactic latitude of the source, well away from the Galactic \nBulge, and the shape of its light curve suggest that it is a \ngamma-ray burst with a very unusual spectrum, perhaps similar to \nthose reported for \"X-ray rich\" GRBs by Heise et al (2001) from \nBeppoSAX observations.  Conceivably, it could instead be a nearby \nX-ray burst source.  A preliminary catalog search of the WXM error \ncircle revealed no correspondence with known globular sources, \ncataclysmic variables, low mass X-ray binaries, or flare stars.\n\nFollow-up observations of this unusual transient are encouraged.\n\nAdditional information on the 13 February high energy transient \n(including light curves, the WXM error box and results from the \npreliminary catalog searches), as well as the HETE mission, is \navailable at:\n\nhttp://space.mit.edu/HETE/\n\nAcronyms:\nHETE=High Energy Transient Explorer\nFREGATE=French Gamma Ray Telescope\nWXM=Wide Field X-ray Monitor\nSXC=Soft X-ray Camera\n\nThis message may be cited.",
  "circularId": 934,
  "createdOn": 982198147000,
  "email": "grr@space.mit.edu",
  "subject": "GRB010213 detected by HETE",
  "submitter": "George Ricker at MIT  <grr@space.mit.edu>",
  "eventId": "GRB 010213"
}